Blind participants have been shown to be able to memorise and subsequently navigate a complex route within a large-scale building

Blind participants have been shown to be able to perform judgements of distance between pairs of familiar places as accurately as sighted individuals

Bryne and Salter, 1983

4

Bryne and Salter, 1983

Blind participants have been shown to be able to perform judgements of distance between pairs of familiar places as accurately as sighted individuals

Blind people performed worse than sighted people when describing the direction of familiar places from home and poorer again, when describing the direction from an imaginary location

5

Blind participants were able to recall and replace objects in their locations of a round table/board

Hollins and Kelly, 1988

6

Hollins and Kelly, 1988

Blind participants were able to recall and replace objects in their locations of a round table/board

7

each of these studies also found limitations: Blind individuals required more planning details and decisions to wayfind, suggestive of greater cognitive effort.

Passini and Proulx, 1988

8

Blind people performed worse than sighted people when describing the direction of familiar places from home and poorer again, when describing the direction from an imaginary location

Bryne and Salt, 1983

9

(two references) Blind people experienced difficulty updating their cognitive map of the layout of objects when their own relative position/perspective had changed

(Hollins and Kelley, 1988; Riesar, Guth, and Hill, 1986).

10

Network map is?

In a network maps routes are encoded as strings of nodes (a location), each node may have an embedded instruction to be acted upon when that node is reached (e.g., turn left); this allows estimations of distance but those of direction are difficult due to the reliance of relative bearings (e.g., left, right).

11

Vector map is?

a vector-map that contains information about both locations and their location in space, and uses allocentric bearing (North, south, east, west), is required to estimate direction from an out of sight or imaginary location.

12

Visually impaired are able to spatially-update when allowed to physically replace objects in a location that they have felt (REFERENCE 1), but not when they have only locomoted to an object(REFERENCE 2)

R1: Hollins and Kelley, 1988

R2: Riesar, Guth and Hill, 1986

13

early- Blind participants found it no easier to spatial-update when locomoting to a new perspective point than when they imagined it (late blind and sighted people found locomoting helpful.)

Riesar, Guth and Hill, 1986

14

However, these do not necessarily reflect deficiency as much as functional difference and unfavourable environments that have a relative abundance of visual prompts over haptic or auditory aids.

For example, congenitally and early blind children had innate difficulty using a tactile map to infer distance between objects – but with training in ratio-scaling were able to perform as well as their sighted peers.

Unger, Blades and Spencer, 1997

15

Individuals with visual impairments may also have a preference for egocentric reference systems for both direction (e.g., left, right over north, west) and distance (e.g., number of steps over meters) because this reflective of the close-space nature of haptic experience.

Kalia et al. 2010

16

Kalia et al. 2010

Individuals with visual impairments may also have a preference for egocentric reference systems for both direction (e.g., left, right over north, west) and distance (e.g., number of steps over meters) because this reflective of the close-space nature of haptic experience.

17

Assessment of indoor route-finding technology for people with visual impairment

Kalia et al. 2010

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Teaching children to use a tactile map

Unger, Blades and Spencer, 1997

19

Wayfinding in a large-scale building

Passini and Proulx, 1988

20

Memorising the location of objects on a table

Hollins and Kelly, 1988

21

Distance and direction of familiar place pairs

Bryne and Salt, 1983

22

Spatially updating and locomoting/imagining perspective changes in a room with objects

Riesar, Guth and Hill, 1986

23

Overview paper

Performance of blind individuals in many behaviours and tasks requiring imagery can be inferior to that of sighted subjects suggestive of a deficiency theory– the notion that the congenitally blind simply lack certain spatial skills, because they lack the visual experience necessary to develop them. However, surprisingly, despite limited or no visual experience blind individuals do appear to have the capacity for mental imagery. For example, blind individuals (as in sighted individuals) have a stronger memory for concrete, imaginable (i.e., possible to picture), words over abstract (non-imaginable words). Similarly, the laws of perspective appear to be present in the mental imagery of blind individuals. This is further reflected in the successful performance of spatial tasks, such as way-finding and memory for spatial layouts. Since blind individuals lack visual perception, their ability to perform well in tasks requiring the mental representation of space suggests that different cognitive mechanisms and compensatory mechanisms may help overcome visual impairment – as suggested by the qualitative difference theory.The case for qualitative difference theory first requires dismissing the notion that mental imagery is a mere copy of visual input, as although there is cortical overlap between visual perception and imagery, they are not one and the same. Visual imagery requires a network of spatial subsystems and is likely the end product of a series of constructive processes that utilise different sources of information. In fact, visual cortical areas can be activated by objects presented in non-visual sensory modalities (e.g., touch). In the case of severe visual deprivation profound reorganisation phenomena occurs, such that areas originally devoted to process visual information are largely recruited by other sensory modalities (e.g., haptic, auditory). This suggests that visual perception may not, in fact, be required to develop mental representation of space.